This invention relates to cannulae for the introduction and withdrawal of fluids from body cavities such as the peritoneum, vena cava, veins, arteries, heart chambers.
Introduction of tubing for the introduction and withdrawal of fluids from body cavities is well known. Generally, such tubing is termed a cannula or a catheter. An example of the use of a cannula for diagnostic purposes is the determination of blood flow by infusing a dye, allowing dilution and withdrawing a sample. An example of the use of a cannula for therapeutic purposes is the placement of an indwelling catheter connected to an insulin pump. In most procedures, introduction of the cannula is percutaneous or under indirect visualization. A small incision can be made for the insertion of the cannula. For purposes such as those, a single cannula may suffice. For certain procedures, it is desirable to have different channels of introduction and withdrawal to avoid contamination of one fluid with the other, or to allow simultaneous introduction and withdrawal of fluids. Two cannulas may be inserted, but such a procedure would require two incisions and possibly two technicians to monitor and coordinate introduction and withdrawal of fluids; and furthermore, an appreciable distance may be required for optimal efficiacy.
U.S. Pat. No. 4,755,176 discloses a double lumen cannula, with side holes in the outer wall communicating with the vessel in which it is placed. Fluid may be introduced through the tip of the minor lumen, while fluid in the vessel, which has entered through the side holes, may be withdrawn through the outer lumen.
However, a need exists for a dual lumen, adjustable cannula in which the inlet and outlet areas have a separated distance.
The present invention comprises a larger diameter outer cannula with a major lumen, within which resides a fully adjustable smaller diameter inner cannula with a minor lumen, forming a dual cannulae assembly. The inner cannula is of a greater length than the outer cannula and can be advanced within the major lumen to any length necessary to adjust to patient size and vessel length or desired chamber, or to separate the areas of introduction and withdrawal of fluids as required by the procedure. The ability to adjust fully overcomes the current problem of creating an undesirable flow loop with concomitant decreases in efficacy as occurs in a dual lumen cannula that is not adjustable. Each of the lumens is provided with at least one opening at its distal end, which may be at the tip of the cannula but preferably is located on the side wall. Most preferably, each cannula is provided with a plurality of openings placed around the periphery of the cannulae. The cannula assembly may also be fitted with a guide wire to ease insertion. The cannula assembly is inserted percutaneously through a single incision while in the rest position, that is, with the distal ends of the inner and outer cannulae at the same position. Once into the desired body cavity, both are advanced together to the desired area and the inner cannula is then advanced to a farther position as determined by the procedure. Each lumen communicates with a separate external reservoir(s) through a bifurcated joint at the proximal end, which may be fitted with clips, injection ports and the like. The body cavity may be a blood vessel, chamber, i.e. heart, or the peritoneum